On Tue, Jul 14, 2015 at 02:13:23PM -0300, Marcelo Ricardo Leitner wrote:
> Hi,
>
> I'm trying to remove a direct dependency of dlm module on sctp one.
> Currently dlm code is calling sctp_do_peeloff() directly and this call
> only is causing the load of sctp module together with dlm. For that, we
> have basically 3 options:
> - Doing a module split on dlm
> - which I'm avoiding because it was already split and was merged (more
> info on patch2 changelog)
> - and the sctp code on it is rather small if compared with sctp module
> itself
> - Using some other infra that gets indirectly activated, like getsockopt()
> - It was like this before, but the exposed sockopt created a file
> descriptor for the new socket and that create some serious issues.
> More info on 2f2d76cc3e93 ("dlm: Do not allocate a fd for peeloff")
> - Doing something like ipv6_stub (which is used by vxlan) or similar
> - but I don't feel that's a good way out here, it doesn't feel right.
>
> So I'm approaching this by going with 2nd option again but this time
> also creating a new sockopt that is only accessible for kernel users of
> this protocol, so that we are safe to directly return a struct socket *
> via getsockopt() results.
>
> "Kernel users" are identified by sockets that don't have a file
> descriptor attached to it, as only kernel users are allowed to do that
> and, if original socket has a file descriptor, one should just use the
> original option.
>
> I kept __user marker on sctp_getsockopt_peeloff_kernel() prototype and
> its helpers just to avoid issues with static checkers.
>
> I tried minimizing the code duplication while adding the new option, but
> it's just better to add a whole new function to handle it. As the
> sockopt arguments are different, the only thing in common between both
> call handlers is the call to sctp_do_peeloff(). All rest would have to
> have checks around it.
>
> RFC->v1, from Neil:
> - For identifying kernel users, switched from segment_eq() to fd check
> - Reused original option to avoid code duplication
> v1->v2, from David:
> - Back to new sockopt implementation, to avoid changing sockopt arg
> format.
>
>
> Marcelo Ricardo Leitner (2):
> sctp: add new getsockopt option SCTP_SOCKOPT_PEELOFF_KERNEL
> dlm: avoid using sctp_do_peeloff directly
>
> fs/dlm/lowcomms.c | 17 ++++++++---------
> include/uapi/linux/sctp.h | 12 ++++++++++++
> net/sctp/socket.c | 37 +++++++++++++++++++++++++++++++++++++
> 3 files changed, 57 insertions(+), 9 deletions(-)
>
> --
> 2.4.1
>
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Series
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
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